Consumer, business and industrial appliances require third party safety certification, e.g., UL: Underwriters Laboratories Inc., CSA: Canadian Standards Association, ETL: Intertek Testing Services, and/or CE: Conformance European (Communaut Europ enne or Conformit Europ enne), etc. Product certification programs are accredited by the United States Occupational Safety and Health Administration (OSHA), the American National Standards Institute (ANSI), and the Standards Council of Canada (SCC). Certification requires that fault conditions be detected and dealt with in a safe and predictable manner. In a digital device, e.g., a microprocessor, a microcontroller, etc., that uses an internal voltage regulator with an external filter capacitor, there is the possibility that the integrated circuit package pin connected to the external filter capacitor can come in contact, e.g., be short-circuited, with another adjacent package pin having a higher voltage thereon, thereby putting the functionality of the integrated circuit device at risk. This could have dire consequences for operation of the appliance controlled by the integrated circuit device.
The external filter capacitor connection, Vcap/Vddcore, pin may be situated between a higher voltage, Vcc, pin (usually 3 to 3.6 volts) and a ground, Vss, pin. If the Vcap/Vddcore pin should short to ground, Vss pin, then the brown-out-reset (BOR) and/or power-on-reset (POR) circuits will detect a low voltage condition and force the integrated circuit device into a reset state that is well defined. However, if the Vcap/Vddcore pin is shorted to the Vcc pin then the internal logic circuits of the integrated circuit device can degrade to unknown states due to the too high voltage being applied thereto (an unsafe condition). The internal logic circuits are usually designed for an operating voltage of from about 1.8 volts to about 2.5 volts.